Ms. Murray learned of her daughter’s disappearance after receiving a call from school officials who told her social workers got word from students who had received texts from Ashley that said she would kill herself. Her mom later found a note from her daughter, which she called a “suicide note,” saying it made reference to a “watery grave.”

“This was all thought out and planned the night before,” Ms. Murray said.

Southold Police initially employed a marine patrol, its canine unit and a Suffolk County Police helicopter to perform a physical search Monday morning, but later focused their investigation on the possibility that she may have left the area. They then ended the active local search Monday afternoon and began to concentrate on examining phone and computer records, and interviewing close friends and family, police said.

Police did not release an official missing person report until Wednesday morning, more than 50 hours after Ashley’s disappearance. Law enforcement officials said Ashley’s case does not fit criteria for an “Amber Alert,” since she is not believed to have been abducted.

Anyone with information on the whereabouts of Ashley Murray (above) should contact Southold Police at 765-2600.

That did not stop local residents from conducting their own searches and using social media to reach thousands of concerned web surfers from across the country.

A missing poster created Tuesday night by the Facebook page “Missing,” which has a reach of about 125,000 Facebook users, was already shared by more than 14,000 people the following morning, with an additional 1,200 people “liking” the poster and another 1,000 users commenting.

“Shared in Ottawa, Ontario Canada,” one user wrote.

“I encourage everyone to pray for this young girl,” said another commenter.

Locally, friends of Ashley created a Facebook page called “Ashley Come Home,” which was already followed by more than 1,000 Facebook users just hours after its creation. Users shared their photos of Ashley and the page, where they made desperate pleas for their friend to return safely.

“If anyone knows ANYTHING that could help lead to Ashley’s safe return please tell someone as soon as possible! We need to know as much as we can so we can find this beautiful young lady!” the moderator of the page wrote.

Many of her classmates posted that they were out searching locally for their friend, who they said was often bullied in school.

Ashley is 5-foot 4-inches and 140 pounds with reddish-brown hair, her mother said. She was last seen wearing red sweatpants “four sizes too big,” black boots and a zip-up sweatshirt with a hood, Charlotte Murray said. Police added that she has a scar on her right wrist and wears hearing aids in both ears.

“She didn’t even leave with a winter coat,” her mom said, and she left behind medication she must take for anemia.

Ashley’s mom also said her daughter has never run away from home before.

“I’d like for her to come home,” Ms. Murray said, adding that she hadn’t slept since her daughter went missing Monday morning.

Ms. Murray said her daughter’s phone is turned off or not working.

Southold Superintendent David Gamberg said the district has been cooperating with the Southold Police Department since the investigation began Monday.

“We have deep, deep concerns about her whereabouts and her safety,” Mr. Gamberg said. “Anything and everything we can do we will do.”